Free Essay

The Function of Proteins Are Linked to Their Shape

In: Science

Submitted By atotheh
Words 932
Pages 4
The functions of protein are linked to their shape

Proteins are polymers of amino acids joined by strong peptide bonds. The combination of any of the twenty amino acids in any length and sequence allows an almost infinite number of possible structures and functions.

The sequence of amino acids in the polypeptide chain is termed the primary structure. The primary structure is unique to a given protein. The primary structure can fold regularly to form either an α-helix or β-pleated sheet. The secondary structure is held together by hydrogen bonds between adjacent peptide bonds. The primary structure can further fold in an irregular but not random manner to form an overall three dimensional shape that more specifically determines the biological functions of the individual protein. This 3D structure is held together by bonds formed between the R-groups of amino acids.

For movement, animals use muscle contraction. Muscle fibres are composed of two protein filaments, myosin which is a thick filament and actin which is thinner. Actomyosin cross-bridges can form between the two which move relative to one another on hydrolysis of ATP drawing actin into myosin. This sliding filament theory shows how a sarcomere contracts. This contraction is used in a variety of applications including constriction or dilation of blood vessel to modify blood flow through tissues, pupil diameter to control light entry into eyes or the generation of a force at a joint to move a hand away from a hot object.

Some proteins adopt a structural role. For example, keratin, a protein in skin, is formed from coils that twist together to form rope-like structures that are both flexible and strong. This strength is utilised in animals as claws or horns for predation or protection, or hair as camouflage or insulation. Collagen, another important structural protein that comprises connective tissue in animals, is composed of coils that are more tightly bound giving a more rigid structure.

Some proteins adopt a transport role. Channel proteins in cell membranes offer a hydrophilic passage through the hydrophobic lipid bilayer. They have a specific three dimensional shape that is complementary to the given species they transport. For example, sodium gated channels in membranes of sensory neurones allow the passage of sodium into the axon during the generation of an action potential. Similar transport proteins are carrier proteins that can change shape on binding of their transporter molecule, e.g. glucose channel in liver cells to allow glucose to pass through the membrane in preparation for the process of glycogenesis.

Proteins form a key role in the infectivity of pathogens and the immunity of the host. Proteins on the surface of pathogenic bacteria act as antigens which identify a cell as non-host. Some of these antigens can break away and act as toxins. For example, the bacteria Vibrium cholerae releases a protein toxin that opens chloride ion channels in the large intestine causing loss of chloride from epithelial cells, and loss of large volumes of water as diarrhoea and chronic dehydration. Variation in the antigenic structure brought about by mutation of the pathogen’s DNA can increase the infectivity of the pathogen as the host has no memory cells or antibodies to bind to and inactivate the antigen. Phagocytosis of pathogens eventually leads to activation of B-cells

which divide by mitosis forming clones that differentiate to form plasma cells. These cells release antibodies that are globular proteins which have variable regions that have a complementary shape to a specific antigen, allowing it to agglutinate many pathogenic particles.

A key role for proteins is to act as enzymes; biological catalysts that lower activation energy of specific reactions, allowing them to take place under controlled conditions at body temperature. They have an active site that has a specific 3D shape that is complementary shape to a specific substrate. This provides specificity to reactions. On binding, the enzyme and substrate form an enzyme-substrate complex which places strain on the bonds allowing them to break more easily. For example, the enzyme sucrase has an active site that is complementary to the disaccharide sucrose. Lactose, another disaccharide that has a similar but subtly different shape to sucrose, will not fit into this site, and is therefore not hydrolysed by the enzyme. DNA polymerase condenses adjacent DNA-nucleotides together during the formation of the phosphate-sugar backbone of DNA during semi-conservative replication. Despite being similar in structure, RNA-nucleotides require RNA-polymerase to join them during transcription. These reactions highlight the high degree of specificity elicited by the flexible nature of the primary and tertiary structures of proteins.

Chemical coordination in animals is largely brought about using protein hormones. These hormones have a tertiary structure that is complementary to that of a receptor molecule often another protein or glycoprotein positioned on the cell-surface membrane of the target cell. Examples are insulin, a protein released by β-cells of the islets of Langerhan in the pancreas during conditions of high blood sugar concentrations. The insulin travels in the blood to hepatocytes in the liver and binds to a specific membrane receptor that causes activation of phosphorylase enzyme that condense glucose into glycogen in the process of glycogenesis. Glucagon is released from α-cells in the pancreas and stimulates the hydrolysis of glycogen into glucose when blood sugar is low. Other examples of endocrine hormones include follicle stimulating hormone that matures the ova in a follicle during the follicular phase of the menstrual cycle, and luteinising hormone, that causes rupture of the follicle and the release of the ova, once it has matured.

Similar Documents

Premium Essay

Basic Molecule of Cell

... Learning outcomes: 1. Explain how a cell can make a variety of large molecules from a small set of molecules 2. Define monosaccharides, disaccharides, and polysaccharides and explain their functions 3. Define lipids, phospholipids, and steroids and explain their functions 4. Describe the chemical structure of proteins and their importance to cells 5. Describe the chemical structure of nucleic acids and how they relate to inheritance Copyright © 2012 Pearson Education, Inc. Rearrange these in the correct order: INTRODUCTION TO ORGANIC COMPOUNDS © 2012 Pearson Education, Inc. 3.1 Life’s molecular diversity is based on the properties of carbon  Carbon-based molecules are called organic compounds.  Methane (CH4) is one of the simplest organic compounds. – Four covalent bonds link four hydrogen atoms to the carbon atom. – Each of the four lines in the formula for methane represents a pair of shared electrons. © 2012 Pearson Education, Inc. Three representatives of methane (CH4) Structural formula Ball-and-stick model Space-filling model The four single bonds of carbon point to the corners of a tetrahedron. Different bond angles and shapes occur when carbon atoms form double bonds. Hence, a molecule’s shape determines its function 3.1 Life’s molecular diversity is based on the properties of carbon  Compound composed of only carbon and hydrogen are called hydrocarbons.  Carbon, with attached hydrogens (aka......

Words: 4247 - Pages: 17

Premium Essay

Bio 111

...Mohamed M Vocabulary: A | B | alpha (?) helix | The spiral shape resulting from the coiling of a polypeptide in a protein's secondary structure. | amine | An organic compound with one or more amino groups. | amino acid | An organic molecule containing a carboxyl group and an amino group; serves as the monomer of proteins. | amino group | In an organic molecule, a functional group consisting of a nitrogen atom bonded to two hydrogen atoms. | anabolic steroid | A synthetic variant of the male hormone testosterone that mimics some of its effects. | carbohydrate | Member of the class of biological molecules consisting of simple single-monomer sugars (monosaccharides), two-monomer sugars (disaccharides), and other multiunit sugars (polysaccharides). | carbon skeleton | The chain of carbon atoms that forms the structural backbone of an organic molecule. | carbonyl group | In an organic molecule, a functional group consisting of a carbon atom linked by a double bond to an oxygen atom. | carboxyl group | In an organic molecule, a functional group consisting of an oxygen atom double-bonded to a carbon atom that is also bonded to a hydroxyl group. | carboxylic acid | An organic compound containing a carboxyl group. | cellulose | A large polysaccharide composed of many glucose monomers linked into cable-like fibrils that provide structural support in plant cell walls. | chitin | A structural polysaccharide found in many fungal cell walls and in the......

Words: 1232 - Pages: 5

Premium Essay

Biology Review

...planet is carbon based * All life is carbon based, so to understand how biological processes occur we need to consider organic chemistry Hydrocarbons: molecules that are entirely made from carbon and hydrogen * Carbon you can get a lot of shape (rings etc) * Mostly non-metals (hydrogen, carbon, oxygen etc) make up molecules in our cells * Hydrogen, carbon, nitrogen, oxygen make 96% of living organisms however 21 elements found as well * Most of 4% consists of calcium, potassium, phosphorus, sulfur, sodium, chlorine, magnesium Functional Groups * Most functional groups are ionic or strongly polar which makes them very attracted to other ionic or polar molecules * Non polar portions do not attract other molecules so do not help initiate chemical reactions * So, some polar functional groups are strongly attracted to water and so can often be dissolved in the cytosol of the cell, example ethane is hydrocarbon doesn’t have functional group so does not dissolve in water and is gas at room temperature however ethanol has functional group so highly soluble in water Carbon Chemistry * Because it has has 4 electrons in shell so can form 4 covalent bonds to form these shapes * Can form bonds with others but can also bind with each other * Carbon containing rings can join to make polymers Dehydration and Hydrolysis Reactions; Also Other Reactions * Many reactions, functional groups gain/lose H+/OH- the......

Words: 2456 - Pages: 10

Premium Essay

By1 Essays

...non-competitive * Both types of inhibitors reduce the rate of reaction * Competitive inhibitor is structurally similar and competes with substrate for active site of enzyme * This prevents substrate from binding to the active site * Fewer/ no enzyme-substrate complexes formed * If substrate concentration is increased in reduces the effect of the inhibitor. * Non-Competitive inhibitor binds away from the active site * This alters the overall shape of the enzyme, including active site * Substrate and inhibitor are not competing for the same active site * Therefore increasing substrate concentration will have no effect of rate of reaction * Enzymes tolerate wider range of conditions such as temperature/ph * Enzymes are easily reused thus reducing costs * Several enzymes can be used together * Product is not contaminated * Enzymes are easily added or removed Describe the functions and importance of mitosis to living organism using example where appropriate Describe how meiosis differs from mitosis and explain the significance of these differences * Mitosis results in daughter cells that are genetically identical * That have the same number of chromosomes as the parent cell * The division allows the production of cells that are genetically identical to the parent and so gives genetic stability * By producing new......

Words: 951 - Pages: 4

Premium Essay

Nfm Alemoa

...Explain and give examples of why proteins are essential to cell function * The basic structure of an amino acid * Describe the 4 levels of protein structure, and give examples of each * Explain what an enzyme is, understand why enzymes are needed to help chemical reactions, and know the role of the active site * Revisiting the Theory of Chemical Evolution * Modern life arose through a series of endergonic chemical reactions. 1. Production of small organic compounds * i.e., formaldehyde (H2CO), hydrogen cyanide (HCN) 2. Formation of mid-sized molecules from these small compounds * i.e., amino acids, simple sugars 3. Mid-sized building blocks combine to form large molecules. * i.e., proteins, complex carbohydrates 4. Life became possible when one of these large molecules self-replicated. * Organic Molecules * Large organic molecules are called macromolecules * Four major categories of macromolecules: 1. Proteins 2. Nucleic Acids 3. Carbohydrates 4. Lipids * Several of these are long chains of smaller subunits. * The smaller subunits are known as monomers * The long chains of monomers are known as polymers * Four groups of Macromolecules * Building Macromolecules – Monomers and Polymers * Molecules, such as amino acids, are individual units called monomers. They link together (polymerize) to form polymers, such as proteins. *......

Words: 1630 - Pages: 7

Premium Essay

Mr and Mrs

...or more long chains of amino acid residues. Proteins perform a vast array of functions within living organisms, including catalyzing metabolic reactions, DNA replication, responding to stimuli, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20-30 residues, are rarely considered to be proteins and are commonly called peptides, or sometimes oligopeptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residues in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the genetic code specifies 20 standard amino acids; however, in certain organisms the genetic code can include selenocysteine and—in certain archaea—pyrrolysine. Shortly after or even during synthesis, the residues in a protein are often chemically modified by posttranslational modification, which alters the physical and chemical properties, folding, stability, activity, and ultimately, the function of the proteins. Sometimes proteins have non-peptide groups attached, which......

Words: 2229 - Pages: 9

Premium Essay


...2.3 Chemistry of water Water is a polar molecule The shape of a water molecule and its polarity make hydrogen bonding possible, A hydrogen bond is a weak attraction between a slightly positive hydrogen atom and a slightly negative atom. (They are partial charging) * Can occur between atoms of different molecule or within the same molecule * A single hydrogen bond is easily broken while multiple hydrogen bonds are collectively quite strong. * Help to maintain the proper structure and function of complex molecules such as proteins and DNA. Oxygen attracts the shared electric and is partially negative Hydrogens are partially positive. Properties of water * Water molecules cling together because of hydrogen bonding * This association gives water many of its unique chemical properties * Water has a high heat capacity * The presence of many hydrogen bonds allow water to absorb a large amount of thermal heat without a great change in temperature * The temperature of water rises and falls slowly * Allows organisms to maintain internal temperatures. * Water has a high heat of vaporization * Hydrogen bonds must be broken to evaporate water. * Bodies of organism cool when their heat is used to evaporate water. * Water is a good Solvent * Water is good solvent because of its polarity * Polar substances dissolve readily in water * Hydrophilic molecules dissolve in water (sugar) ...

Words: 4521 - Pages: 19

Premium Essay

Biology Review

...Review Biology Test #1 Chapter 3: Water and life • Polar covalent bonds in water result in Hydrogen bonding between the molecules. These bonds give water its special properties • In presence of water, ionic bonds are weak and covalent bonds are strong. Without water, ionic bonds are stronger. • Each water molecule can make 4 hydrogen bonds. • Water properties: 1. Polarity 2. Surface tension 3. Cohesion 4. Adhesion 5. Capilarity 6. High specific heat 7. Heat bank 8. Heat of vaporization allows evaporation cooling. 9. Abundant and versatile solvent 10. Solid is less dense than liquid 11. It is a reactant and a product in many biological reactions (Photosynthesis, dehydration reaction, hydrolysis…) 12. It can ionize into H3O+ and OH- • When substances dissolve in water, water molecules form hydration shells by breaking their attractions to other water molecules and attracting to the solvate particles. • The dissociation of water molecules into Hydronium and hydroxide ions is a reversible reaction that occurs in a state of equilibrium (pure water). • The concentration of each ion in pure water is 10-7 M. [OH-][H3O+] = 10-14 M. This way, whenever we know the concentration of one ion, we can calculate the concentration of the other. • Adding acids and bases can change these concentrations of ions in water • When acids dissolve in water, they donate H+, increasing the concentration of hydrogen ions. This results in an acidic solution • When bases dissolve in......

Words: 5464 - Pages: 22

Premium Essay

Dna Medical Level 3

...1.Define the primary structure The primary structure is a polypeptide chain of amino acids linked with peptide bonds. 2. Describe how the DNA sequence defines the amino acid sequence in the primary structure The structure of the dna is very important ,it has specifc order.if one gets moved or is incorrect it can cause mutation. Different 3 base pairs codes form different amino acids. The amino acids then are linked in the order that they appear in a section of DNA into protiens. The formation of the amino determines how the proteins folds and twists which controls the overall shape. The shape has to be precisely right or the protein will not function properly. If you have any Deformed proteins they can cause a person to be lactose intolerance, sickle cell animia and to have some allergies. 3. Identify the groups in an amino acid. 1.Amino group 2.R Group (Side chain) 3.Carboxyl group 4. Identify and describe the reaction shown in the diagram. A Water molecule is removed by condensation between the carboxyl. 5. Describe the role of the peptide backbone, variable side chains and the bonds holding the primary structure together. Polypeptides and proteins are chains of amino acids held together by peptide bonds. 6. Define the secondary structure. Secondary structures are polypeptide chains folded into one of two configurations: either an alpha helix, or a beta pleated sheet. 7.......

Words: 278 - Pages: 2

Premium Essay

Biology Notes

...components of life such as cells, DNA, RNA) is used to solve crimes and reveal ancestry. Ecology- The scientific study of interactions among organisms and their environment is used to address environmental issues. Neuroscience- Field in biology that deals with brains; and Evolutionary science- the study of the evolution of organisms are being used to reshape psychology and sociology. Characteristics of Life: Living things are organized – The organs or vital components that make up a living organism each perform a specific function in an organized way such that it allows the organism to live. Regulation – All living organisms have the ability to regulate and accommodate to changes in their environment in order to stay alive. Growth and Development – Living organisms have the ability to grow and develop. Energy Utilization – Living organisms use energy or convert energy from a food source in order to carry or be able to perform different functions. For example, the human body utilizes carbohydrates found in food as a source of energy. With this energy, humans are able to perform simple tasks such as walking, talking, breathing, etc. Response to environment – Similar to regulation, living organisms have the ability to interact with the environment. For example during winter seasons, humans wear heat-retaining garments to protect them from the cold. Similarly, bears hibernate during the winter season, birds migrate, etc. Reproduction – The ability to reproduce or......

Words: 6992 - Pages: 28

Premium Essay


...BIOLOGY UNIT 2 F212 Describe how hydrogen bonding occurs between water molecules, and relate this, and other properties of water, to the roles of water in living organisms (HSW1); A water molecule is made up of two hydrogen bonds and one of oxygen. The atom forms a triangular shape, although the molecule has no overall charge, the distribution of negatively charged electrons is uneven because the oxygen atom draws them away from the hydrogen. This consequently makes oxygen slightly negative while hydrogen has a slightly positive charge. We call this a dipolar molecule. Hydrogen bond Different poles attract , therefore the positive pole of one water molecule will attract the negative pole of another water molecule. The force of attraction between the opposite charges are known as hydrogen bonds. Although the bond is weak it forms important forces that gives water its properties. Properties of water * Specific heat capacity: because water molecules stick together it takes more energy to break them apart, for this point the boiling point of water is higher than expected. Water there for acts as a buffer against sudden temperature variations, making the aquatic environmental temperature stable * Cohesion and surface tension: the tendency of molecules sticking together is known as cohesion. With its hydrogen bonding water has large cohesive forces and these allow it to be pulled together through a tube such a xylem vessel in plants. * Density of water: water...

Words: 1932 - Pages: 8

Premium Essay


...Structure and Function The word protein was first coined in 1838 to emphasize the importance of this class of molecules. The word is derived from the Greek word proteios which means "of the first rank". This chapter will provide a brief background into the structure of proteins and how this structure can determine the function and activity of proteins. It is not intended to substitute for the more detailed information provided in a biochemistry or cell biology course. Proteins are the major components of living organisms and perform a wide range of essential functions in cells. While DNA is the information molecule, it is proteins that do the work of all cells - microbial, plant, animal. Proteins regulate metabolic activity, catalyze biochemical reactions and maintain structural integrity of cells and organisms. Proteins can be classified in a variety of ways, including their biological function (Table 2.1). Table 2.1 Classification of Proteins According to biological function. | Type: | Example: | Enzymes- Catalyze biological reactions | ß-galactosidase | Transport and Storage | Hemoglobin | Movement | Actin And Myosin in muscles | Immune Protection | Immunoglobulins (antibodies) | Regulatory Function within cells | Transeription Factors | Hormones | Insulin Estrogen | Structural | Collagen | How does one group of molecules perform such a diverse set of functions? The answer is found in the wide variety of possible structures for proteins. In......

Words: 3612 - Pages: 15

Premium Essay

Biochemistry Task 2

...Biochemistry Task 2 October 17, 2015 (Yatherajam, 2015) (Yatherajam, 2015) Organic Compounds. Retrieved October 16, 2015, from Notes D organic chem.htm Polypeptides (n.d.) Retrieved October 16, 2015, from Pepsin Enzyme: Structure, Function, and Important Facts. (2014, September 25). Retrieved October 16, 2015, from There are four forces, both bonds and interactions, which help stabilize or hold together a tertiary structure.  These four forces include hydrophobic interactions, hydrogen bonds, ionic bonds, and disulfide bonds.  Hydrophobic interactions are the weakest of the four forces and they occur between nonpolar amino acids.  According to Borges (2014) these hydrophobic interactions occur in amino acids such as leucine and phenylalanine.  The amino acids involved in hydrophobic interactions are amino acids which are not capable of hydrogen bonding.   The next force is hydrogen bonding, which occurs between polar or charged amino acids like tyrosine and aspartate, according to Borges (2014).  At the oxygen level the amino acids share their hydrogen atom with one another, one hydrogen atom becomes the donor and the other the recipient.  The hydrogen bond is stronger that...

Words: 929 - Pages: 4

Premium Essay

Anatomy 213

...Two integrated division of study Anatomy: study of the structure of the body; morphology Physiology: study of the function of the body; how does it work Fields of anatomy Gross anatomy: what you can see with the naked eye - Regional anatomy: studying just the head (looking at its muscles, etc) - Systemic anatomy: 11 body systems - Surface anatomy: study superficial anatomy; surface structures, then identify it deeper; surface landmarks Microscopic anatomy: seen with microscope - Cytology: cells - Histology: study of tissues Developmental anatomy: study of changes of the body from conception to full maturation Comparative anatomy Radiographic anatomy: using special tools - CT, NMR, MRI Chapter1 : Page 6- intro to organ systems, different characteristics The Cell Cytology: study of the cell Why study cells? - Cells concentrate needed molecules, expel waste, synthesize larger molecules with complex functions, generate/store/use energy for metabolic processes, move (transport) - Diseases begin at the cellular level (ex: cells dividing uncontrollably.. cancer) - You are made of 75 trillion cells Cells divided into: - Sex cells: sperms/eggs - Somatic cells: cells of the body Looking at the structure of a cell can show the cell’s function Environment of the cell - Cytoplasm (intracellular fluid) - Cytoplasm (intracellular fluid - Extracellular fluid: usually fluid like, consists of resources  Acts as a cellular freeway.. allows movement of medium...

Words: 1233 - Pages: 5

Premium Essay

Food Web Diagram

...Unit II: Genetics Brief Overview Reading: Chapters 3, 4, 9-12, 14 (Note: you have reviewed much of this already) The earth is teeming with living things. We can easily see some of the larger organisms—trees, grass, flowers, weeds, cats, fish, squirrels, dogs, insects, spiders, snails, mushrooms, lichens. Other organisms are everywhere, in the air, in water, soil and on our skin, but are too small to see with the naked eye—bacteria, viruses, protists (single celled eukaryotes such as amoebae), and tiny plants and animals. Life is remarkable in its complexity and diversity, and yet it all boils down to a very simple idea—the instructions for making all this life are written in nucleic acids, usually DNA. Most organisms have a set of DNA that contains the instructions for making that creature. This DNA contains four “letters” in which these instructions are written—A, T, G, and C. The only difference between the code for a dog and the code for a geranium is in the order of those letters in the code. If you took the DNA from a human and rearranged the letters in the right way, you could produce an oak tree—arrange them slightly differently and you would have a bumble bee—arrange them again and you would have the instructions for making a bacterium. Acting through more than two billion years, the process of evolution has taken one basic idea—a molecular code that uses four letters—and used it over and over, in millions of combinations to produce a dazzling array of life......

Words: 32016 - Pages: 129